Exploring more than 120 years of medical discovery, clinical trials and the evolving science of photobiomodulation.
Why This Research Is So Personal to Me
A mother’s experience that changed my perspective on light therapy
Before exploring more than 120 years of scientific research into light therapy, I would like to share the personal experience that first made this subject so important to me.
In 2020, my daughter developed facial palsy.
What initially appeared to be a problem affecting the movement of her face turned out to be something far more serious.
Her facial palsy prompted us to seek hospital care, where doctors discovered that she had contracted Lyme disease following a tick bite.
Further investigations, including a lumbar puncture, revealed that she had also developed bacterial meningitis.
We spent six weeks in hospital.
As a mother, watching your child go through such a serious illness is an experience that stays with you forever.
I remain grateful that her facial palsy led us to seek medical attention and that the doctors identified the underlying infections.
During her recovery, we also used photobiomodulation with a BIOPTRON light therapy device.
I watched my daughter’s facial function gradually improve, and she eventually recovered from the palsy completely.
I have always felt that light therapy made a positive contribution to her recovery.
Seeing her recovery sparked something in me.
I wanted to understand more about light therapy. How does light interact with our cells? Why are researchers investigating different wavelengths? And what does the published scientific evidence actually tell us?
The more I explored, the more fascinated I became.
I discovered that therapeutic light was not simply a recent wellness trend.
In fact, in 1903, Danish physician Niels Ryberg Finsen was awarded the Nobel Prize in Physiology or Medicine for his pioneering work using concentrated light to treat a form of skin tuberculosis.
More than a century later, photobiomodulation continues to be investigated in clinical trials, systematic reviews and medical research institutions around the world.
Today, as the founder of Yassou-Me Wellness Clinic in Exeter, that personal journey remains one of the reasons I am so passionate about bringing advanced light-based wellness technology to our community.
Our nine-wavelength infrared therapy bed, with a manufacturer-stated irradiance of 160 mW/cm², represents a different technology from the BIOPTRON device we used in 2020. I believe it is important to understand the evidence for each technology individually.
My daughter’s experience inspired my interest.
Science, clinical research and a commitment to understanding the evidence are what continue to drive that interest today.
I would now like to share some of the published research that has shaped my understanding – beginning with the Nobel Prize of 1903 and continuing through modern clinical trials and scientific reviews.
Light has been studied and used in medicine for well over a century. What began with pioneering treatments for serious skin diseases has developed into an expanding field of research investigating pain, inflammation, tissue repair, neurological conditions, skin health and physical recovery.
Today, scientists around the world continue to investigate how specific wavelengths of light interact with biological tissues and whether these interactions can produce meaningful health benefits.
At Yassou-Me Wellness Clinic, our interest in this science is part of our commitment to bringing advanced wellness technology to Exeter.
We believe that understanding the research is just as important as experiencing the technology itself.
This article explores the historical foundations of medical light therapy, the clinical evidence available today, and the important questions researchers are still working to answer.
1. Where It All Began: The 1903 Nobel Prize
Niels Ryberg Finsen and the Birth of Modern Phototherapy
In 1903, Danish physician Niels Ryberg Finsen received the Nobel Prize in Physiology or Medicine for his pioneering use of concentrated light radiation to treat lupus vulgaris, a form of tuberculosis affecting the skin.
His work demonstrated that carefully controlled light exposure could have genuine therapeutic applications.
At a time when treatment options for tuberculosis were limited, this represented an extraordinary medical achievement.
Finsen’s work helped establish phototherapy as a legitimate area of medical investigation.
More than 120 years later, researchers continue exploring the biological effects of light.
It is important to recognise that Finsen’s historical treatments were different from modern red and near-infrared photobiomodulation. Nevertheless, his achievement marks a significant milestone in the medical history of therapeutic light.
Published references:
- The Nobel Prize in Physiology or Medicine 1903 — Official Nobel Prize website
- The History of Phototherapy: Something New Under the Sun? — PubMed
- From Patient to Discoverer: Niels Ryberg Finsen — PubMed
2. What Is Photobiomodulation?
Photobiomodulation, commonly abbreviated to PBM, refers to the use of specific wavelengths of visible red or near-infrared light to influence biological processes.
Researchers are investigating how light absorption within cells may affect mitochondrial signalling, cellular metabolism, inflammatory pathways and tissue responses.
Unlike ultraviolet tanning, photobiomodulation does not depend on ultraviolet exposure.
It is also important to distinguish photobiomodulation from infrared heat therapy. Infrared warmth can have physiological effects through heating, while PBM research often investigates non-thermal cellular responses.
Although both may be incorporated into modern wellness equipment, they are not scientifically interchangeable.
The effects of PBM depend on several factors, including:
- Wavelength of light
- Irradiance and delivered energy
- Duration and frequency of treatment
- Area of the body exposed
- Type of equipment and treatment protocol
- Individual health circumstances
These differences help explain why some clinical studies report positive findings while others show limited or no measurable benefit.
Understanding Irradiance and Light Dosage
One important measurement in photobiomodulation research is irradiance, expressed in milliwatts per square centimetre (mW/cm²).
Irradiance describes the amount of optical power incident on a particular surface area.
Another measurement is radiant exposure, expressed in joules per square centimetre (J/cm²), which takes into account both irradiance and exposure duration.
These measurements are relevant because the biological response to light may depend on the delivered dose, not simply the brightness or power of the equipment.
More light does not necessarily mean a better outcome. Researchers continue to investigate optimal treatment parameters for different applications.
3. A Major Scientific Review: 204 Clinical Trials and More Than 9,000 Participants
One of the most significant recent publications appeared in August 2025 in the peer-reviewed journal Systematic Reviews.
Researchers conducted an umbrella review combining evidence from 15 meta-analyses, representing 204 randomised controlled trials and more than 9,000 participants.
The research examined 35 health outcomes across 15 disease conditions.
The review identified moderate-certainty evidence of benefits for selected outcomes involving:
- Fibromyalgia-related fatigue
- Disability associated with knee osteoarthritis
- Hair density in androgenetic alopecia
- Certain measures of cognitive function
- Pain associated with burning mouth syndrome
The researchers also examined other conditions, including tendinopathy, neck pain and diabetic foot ulcers.
These findings are encouraging, however, they do not establish that photobiomodulation is the most effective for every condition or with every device. The authors called for further well-designed trials and more standardised treatment protocols.
The significance of this review lies not only in its findings, but also in the scale of scientific investigation represented by the underlying clinical trials.
Photobiomodulation is no longer a subject supported only by isolated experiments. It is an established field of scientific investigation involving researchers across multiple countries and medical disciplines.
Published research:
- Son et al. (2025) — Effects of Photobiomodulation on Multiple Health Outcomes: An Umbrella Review of Randomized Clinical Trials
- Read the full open-access publication
4. Pain Management, Osteoarthritis and Fibromyalgia
Pain-related conditions are among the most extensively investigated applications of photobiomodulation.
Knee Osteoarthritis
Research has examined whether PBM may help reduce pain and improve physical function in people living with knee osteoarthritis.
A 2024 systematic review and meta-analysis of placebo-controlled trials reported encouraging pain-related findings, although the authors considered the certainty of the evidence low.
A separate 2025 randomised controlled trial investigated 790 nm laser treatment and reported improvements in selected pain and functional outcomes.
These studies suggest potential as a complementary intervention, not a full replacement for established medical care.
Clinical publications:
- 2024 — Knee Osteoarthritis: Systematic Review and Meta-Analysis
- 2025 — Randomised Controlled Trial Investigating 790 nm Laser Therapy
Fibromyalgia
Fibromyalgia can involve persistent widespread pain, fatigue, sleep difficulties and reduced physical function.
The major 2025 umbrella review identified moderate-certainty evidence for improvement in fibromyalgia-related fatigue with PBM interventions.
This is an important finding because fatigue can substantially affect everyday life.
Published research:
5. Multiple Sclerosis: An Emerging Area of Research
Multiple sclerosis (MS) is a neurological condition affecting the central nervous system.
In September 2024, researchers published a systematic review in Frontiers in Neurology investigating photobiomodulation in relation to MS.
The review included eight studies, four involving human participants and four involving animal models.
Researchers examined outcomes relating to inflammation, oxidative stress, neurological function and other biological processes associated with MS.
Some human studies reported improvements in particular symptoms or functional measures, while experimental studies explored potential biological mechanisms.
The authors described PBM as a promising area for further investigation.
What Did the Researchers Investigate?
The human studies included different wavelengths and treatment approaches, including:
- 650 nm red light
- 808 nm near-infrared light
- 830 nm near-infrared light
- Combinations involving 640 nm, 875 nm and 905 nm
Some studies reported improvements in functional status, muscle strength or pain-related outcomes.
Other research investigated changes in biological markers associated with inflammation.
The inclusion of these different wavelengths is particularly interesting because it illustrates the importance of precise light parameters in clinical research.
However, the evidence remains preliminary. Larger, higher-quality human trials are needed to establish effectiveness, safety over time and appropriate treatment protocols.
Published research:
- Oliveira de Andrade Filho et al. (2024) — Systematic Review of Photobiomodulation for Multiple Sclerosis
- PubMed record
6. Wound Healing and Tissue Repair
The potential role of photobiomodulation in tissue repair has attracted considerable scientific attention.
Researchers have investigated its effects on wound-healing processes, including studies involving diabetic foot ulcers.
A 2016 systematic review examined four randomised controlled trials involving 131 participants.
Subsequent reviews and clinical trials have continued investigating whether light-based interventions may improve wound healing when used alongside conventional treatment.
A 2024 meta-analysis covering 28 studies and 1,471 patients reported favourable outcomes for red and infrared light interventions in diabetic foot ulcer care.
Why Is This Area of Research Important?
Wound healing involves a complex sequence of biological events, including inflammatory responses, cellular activity, tissue regeneration and vascular processes.
Researchers are investigating whether specific light exposures may influence some of these mechanisms.
Although findings are encouraging, wound management is complex, and study quality, treatment parameters and clinical supervision are important.
PBM should not replace professional wound assessment, infection management or established diabetic foot care.
Published research:
- 2016 — Systematic Review of Light Therapy for Diabetic Foot Ulcers
- 2017 — Cochrane Review of Phototherapy for Diabetic Foot Ulcers
- 2020 — Meta-Analysis of Clinical Trials on Diabetic Foot Ulcers
- 2024 — Double-Blind Placebo-Controlled Trial of 904 nm PBM
- 2024 — Meta-Analysis of Red and Infrared Light for Diabetic Foot Ulcers
7. Sports Performance, Muscle Function and Recovery
Photobiomodulation has also been investigated in sports science.
Researchers have explored whether applying red or near-infrared light before or after physical activity may influence muscle fatigue, performance or recovery.
Several systematic reviews have examined localised PBM interventions, with some reporting improvements in specific performance measures.
What About Whole-Body Infrared Therapy?
A particularly relevant systematic review was published in January 2025 in Lasers in Medical Science.
It examined whole-body photobiomodulation in physically active participants.
The review identified five studies involving 105 people.
Two studies reported improvements in sleep-related measures. However, the review did not find evidence of improved exercise performance or fatigue biomarkers.
This distinction matters.
Positive results from a small laser applied directly to a muscle cannot automatically be assumed to occur with a full-body infrared bed.
Whole-body PBM remains an active area of scientific investigation.
Why Recovery Research Matters
Physical recovery is important not only for professional athletes but also for recreational exercisers, physically demanding occupations and people maintaining an active lifestyle.
Understanding whether specific light exposures influence fatigue, muscle function and recovery may eventually help researchers develop more precisely targeted protocols.
For now, the available findings support continued investigation rather than universal claims of faster recovery or improved athletic performance.
Published research:
- 2013 — Review of PBM for Exercise Performance and Recovery
- 2018 — Systematic Review of Muscle Performance and Fatigue
- 2022 — Review of Photobiomodulation and Physical Performance
- 2025 — Whole-Body PBM for Exercise Performance and Recovery
- 2025 — Full Publication in Lasers in Medical Science
8. Skin Health, Hair Growth and Dermatology
Light-based treatments have been investigated in dermatology for decades.
One area with encouraging clinical evidence is androgenetic alopecia, a common form of hair loss.
A 2018 randomised, double-blind, sham-controlled clinical trial involving 100 participants investigated low-level light therapy for hair regrowth.
Researchers reported statistically significant improvements in hair-related outcomes compared with sham treatment.
The 2025 umbrella review also identified moderate-certainty evidence for improvements in hair density.
Beyond Hair Growth
Research into skin ageing, collagen-related processes and other dermatological applications continues.
Scientists are examining how different wavelengths of light may influence cellular signalling and processes involved in skin maintenance and repair.
However, the quality and consistency of evidence differ considerably by indication.
These findings should not be interpreted as proof that every infrared device will improve hair growth, reverse skin ageing or treat specific dermatological conditions.
The particular wavelength, dose, device design and treatment protocol remain important considerations.
Published research:
- 2018 — Randomised Controlled Trial of Low-Level Light Therapy for Hair Growth
- 2025 — Umbrella Review Including Androgenetic Alopecia
9. Is Light Therapy Recognised by UK Medical Authorities?
An important question is whether light-based treatments have any place in evidence-based medicine.
The answer is yes – for certain indications and under defined clinical protocols.
In May 2018, the National Institute for Health and Care Excellence (NICE) published guidance on low-level laser therapy for preventing or treating oral mucositis associated with chemotherapy or radiotherapy.
Oral mucositis is a painful complication that can occur during cancer treatment.
The guidance, originally published as IPG615 and subsequently designated HealthTech Guidance 472, concluded that the available evidence was adequate to support the procedure under standard arrangements for clinical governance, consent and audit.
International clinical guidelines published in 2020 also recommend specific PBM protocols for preventing oral mucositis in certain cancer treatment settings.
Why This Matters
This is an important example of light-based treatment being evaluated through formal medical evidence-review processes.
It demonstrates that photobiomodulation is not categorically excluded from mainstream healthcare.
However, recognition for one medical indication does not establish effectiveness for unrelated conditions or different equipment.
Medical acceptance depends on the quality of evidence for a specific application, the treatment protocol and the balance of potential benefits and risks.
Official clinical references:
- NICE — Low-Level Laser Therapy for Oral Mucositis, HealthTech Guidance 472
- 2020 — MASCC/ISOO Clinical Practice Guidelines for Management of Oral Mucositis
10. What Does This Research Mean for Yassou-Me Wellness Clinic?
At Yassou-Me Wellness Clinic in Exeter, we have invested in an advanced, medical-grade, nine-wavelength infrared therapy bed as part of our commitment to innovative wellness technology.
Our equipment has a manufacturer-stated irradiance of 160 mW/cm².
This is an important technical specification because irradiance is one of the parameters used in photobiomodulation research to describe light intensity at a defined surface.
Understanding Our Infrared Bed’s Specifications
Our infrared therapy bed incorporates nine wavelengths, allowing it to deliver a combination of light wavelengths within a single system.
Its stated irradiance of 160 mW/cm² provides a measurable reference point for understanding optical output.
When irradiance remains constant at the treatment surface, radiant exposure can be calculated by multiplying irradiance by treatment duration.
For illustration:
| Exposure time | Theoretical radiant exposure |
|---|---|
| 5 minutes | 48 J/cm² |
| 10 minutes | 96 J/cm² |
| 15 minutes | 144 J/cm² |
| 20 minutes | 192 J/cm² |
These figures are mathematical illustrations based on 160 mW/cm² and are not verified doses delivered to individual clients.
Actual exposure depends on measurement conditions, distance from the light source, treatment positioning, wavelength distribution and other equipment characteristics.
The total irradiance also does not tell us how much energy is emitted at each of the nine wavelengths.
Importantly, higher irradiance does not automatically mean greater clinical effectiveness.
Research suggests that optimal photobiomodulation parameters may vary depending on the biological tissue and the intended application.
Why We Have Invested in This Technology
Our interest lies in combining technological innovation with an informed understanding of the scientific literature.
The breadth of published research is encouraging, particularly in areas such as selected pain-related conditions, fatigue, skin and hair health, and certain supportive-care applications.
But we also recognise that clinical evidence is specific to the devices, wavelengths, doses and treatment protocols investigated.
A study involving one type of laser or LED device does not necessarily demonstrate that another device will produce identical results.
That is why we believe in discussing both the potential benefits and the limitations of the available research.
We do not believe responsible wellness innovation requires exaggeration.
We believe it requires curiosity, investment, education and respect for evidence.
Our Approach to Wellness
Yassou-Me is developing as a destination for advanced wellness and recovery technologies in Exeter.
Alongside our infrared therapy bed, our facilities include infrared-assisted exercise equipment, hydrogen therapy and hyperbaric oxygen therapy.
These technologies have different mechanisms, research bases and safety considerations, and each should be evaluated on its own evidence.
Our objective is to provide clients with access to innovative equipment in a welcoming, professional environment while continuing to follow developments in scientific research.
11. The Future of Photobiomodulation Research
From Finsen’s Nobel Prize in 1903 to contemporary systematic reviews encompassing thousands of participants, the scientific investigation of therapeutic light has evolved enormously.
Modern researchers continue to explore:
- Cellular and mitochondrial responses to light
- Pain and inflammatory pathways
- Neurological and cognitive outcomes
- Tissue repair and wound healing
- Dermatological applications
- Sleep and physical recovery
- Optimal wavelengths, doses and treatment protocols
Some applications already have clinical guidance supporting their use in defined circumstances.
Others remain experimental or require more robust clinical evidence.
What Comes Next?
One of the greatest challenges for researchers is establishing standardised treatment protocols.
Studies frequently use different devices, wavelengths, power outputs, treatment durations and application methods.
This makes direct comparisons difficult and can explain differences in reported outcomes.
Future research may help determine which applications benefit most from particular wavelengths and doses, how frequently treatments should be delivered, and which individuals may be most likely to respond.
Larger clinical trials, longer follow-up periods and better reporting of equipment specifications will be important.
What is clear is that photobiomodulation is a serious subject of ongoing scientific investigation – not simply a modern wellness trend.
Our Commitment
At Yassou-Me Wellness Clinic, our aim is to make advanced wellness technologies accessible while encouraging informed decisions.
We welcome scientific discussion, clinical research and collaboration with healthcare and wellbeing professionals.
We believe the future of wellness should be shaped by scientific curiosity, responsible innovation and transparent communication.
The history is fascinating. The research is evolving. And there is still much to discover.
Yassou-Me Wellness Clinic
11 St. Thomas Centre
Exeter, EX4 1DG
Website: www.yassou.me
Medical and Scientific Information Notice
This article is provided for educational purposes and summarises published research conducted using a variety of light-based technologies.
The cited studies involve different wavelengths, irradiances, doses, devices, populations and treatment protocols.
Their findings do not establish that Yassou-Me’s infrared therapy bed produces the same clinical outcomes as the equipment used in those studies.
Our infrared wellness services are not a substitute for medical diagnosis, prescribed treatment or professional healthcare advice.
Anyone with an existing medical condition, particularly a condition requiring ongoing specialist care, should consult an appropriate healthcare professional before beginning a new treatment.
Article reviewed: October 2026
